Prior to setting forth the background of the invention in detail, it may be helpful to set forth definitions of certain terms that will be used hereinafter. The term computer-to-plate (CTP) as used herein relates to an imaging technology used in modern printing processes. In this technology, an image created in a desktop publishing application is output directly to a printing plate. CTP as used hereinafter relates also to the imaging device carrying out the process of outputting the computer-stored image to printing plates.
There are different types of printing plates used by CTP imaging devices. Most plates require post processing steps to produce two or three-dimensional features. The present invention refers to the type of plate known as flexographic printing plates. More specifically it refers to a CTP imaging device that is used for direct engraving of a flexography plates utilizing a light source configured from multiple emitters.
Direct engraving of a flexography plates means three-dimensional (3D) carving on the plate material by applied light source energy such as a laser. The concept of direct engraving is remarkably different from two-dimensional imaging techniques which require post processing steps in order to produce three-dimensional features on a plate to be applicable for the flexography market.
FIG. 1 shows a prior art CTP machine for direct engraving of a flexographic plate; multiple emitters array 104 is aligned parallel to the flexographic plate surface 108. The flexographic plate is attached to a rotating drum. For simplicity of the discussion the array of multiple emitters 104 comprises nine emitters. The array of multiple emitters 104 is composed from three groups of emitters 112, 116, and 120, each containing three emitters.
Group 112 emits light 136 on plate surface 108 during first drum revolution 124, group 116 emits light 140 during the second drum revolution 128, and group 120 emits light 144 during the third drum revolution 132. Each of the three groups 112, 116, and 120 in the previous example emit light on the same region of plate surface 108, i.e. pixels p1, p2, and p3 of pixels array 160 are affected by the three groups.
Additionally, during the second drum revolution 128 the first group of emitters 112 emits light 148 on pixels p4-p6. During the third drum revolution 132 pixels p4-p6 are affected by the second group of emitters 116 emitting light 152, while the first group of emitters 112 emit light 156 on pixels p7-p9. The emitters described by the prior art are all imaged just on the surface plane of the flexographic printing plate.
The present invention propose new embodiments concepts for CTP machines, wherein a light source, configured from multiple emitters, is adjusted in a slant or stair configuration relative to the surface plane of the flexographic plate. The slant or stair configuration enables simultaneously imaging different emitters on both the surface plane and at various depths within the printing plate. The multiple emitters are then activated in a way that enhances the direct engraving and ablating effect.